Transmission of working vehicle

ABSTRACT

A transmission for a working vehicle having an engine mounted on a bodywork frame such that a crankshaft of the engine is disposed horizontal and is oriented perpendicular to the longitudinal direction of the vehicle. The transmission comprises an input shaft for receiving power of the engine through a continuously variable transmission, an output shaft disposed in parallel with the input shaft, a pair of left and right axles extended oppositely to each other and in parallel with the output shaft, a differential connecting the left and right axles with each other in a differential manner, a transmission housing containing the differential, a pair of left and right axle housings, each of which houses each of the pair of axles, having mounting portions for mounting to the bodywork frame, and a wet-type disc brake device provided around a portion of the axles covered by the axle housings.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a structure of a transmissioncomprising a belt-type continuously variable transmission (hereafterreferred to as ‘CVT’), which is suitable for a working vehicle.

[0003] 2. Background Art

[0004] A conventional working vehicle, e.g., a truck, includes abelt-type CVT connecting an output shaft of an engine and an input shaftof the transmission such that rotation of the output shaft of the engineis transmitted to its axles and drives them. In this vehicle structure,a sensing mechanism is provided at the CVT and detects rotary speed orload of the engine so as to automatically steplessly reduce/increase thespeed reduction ratio according to the increase/decrease of rotary speedof the engine or the decrease/increase of the engine load.

[0005] In addition, it is well-known to laterally mount an engine on avehicle so as to locate its crankshaft perpendicular to the longitudinaldirection of the vehicle and in parallel to an input shaft of atransmission, an output shaft of the transmission, and axles. Thisdescribed vehicle structure especially facilitates interposing abelt-type CVT between the crankshaft of the engine and the input shaftof the transmission because both shafts are parallel to each other.Moreover, the transmission in this vehicle structure may transmit powervia economical spur wheels because shafts therein are disposed parallelto one another. Therefore, the vehicle structure is advantageous incontributing to the reduction of assembly and material costs.

[0006] An object of the invention is to provide a transmission for aworking vehicle that is simplified so that the manufacturing costs canbe more and more reduced.

[0007] Further, conventional transmissions with differential lockingmechanisms provide a shaft for operating the differential lockingmechanism that is axially, slidably supported and is disposed parallelto the axles. The differential locking slider is engaged with a forkfixed onto the shaft so as to slide the differential locking sliderintegrally with the shaft, thereby switching between adifferential-locking mode and a differential-unlocking mode.

[0008] However, in the above conventional structure, the fork engagedwith the differential locking slider is apt to be large, therebyinhibiting miniaturization of the transmission. And, because a spaceinside of the transmission housing is required for straightly movingsuch a large fork back and forth at a set stroke to operate thedifferential locking slider, further miniaturization of the transmissionis difficult.

BRIEF SUMMARY OF THE INVENTION

[0009] The transmission of the present invention is applied to a workingvehicle having an engine mounted on a bodywork frame such that acrankshaft of the engine is disposed horizontal to the ground and isperpendicular to the longitudinal direction of the vehicle. Thetransmission comprises an input shaft for receiving power of the enginethrough a CVT, an output shaft disposed in parallel with the inputshaft, a pair of left and right axles aligned with and extending outopposite to each other and in parallel with the output shaft, adifferential connecting the left and right axles with each other in adifferential manner, a transmission housing containing the differential,a pair of left and right axle housings mounted onto left and right facesof the transmission housing respectively, each of which houses each ofthe pair of axles, having mounting portions for mounting to the bodyworkframe, and a wet-type disc brake device provided around a portion of theaxles covered by the axle housings. Therefore, a load, which is appliedto drive wheels fixed on the axles, can be supported by the transmissionhousing through the axle housings, thereby simplifying the structure ofa vehicle. And, in comparison with the conventional structure having anoutput of a differential that is transmitted to the drive wheels throughuniversal joints and a dry-type brake device, manufacturing costs can bereduced. Furthermore, due to the wet type disc brake device, durabilityand reliability of the brake device can be improved.

[0010] The input shaft is disposed closer to the engine than said axlesin the longitudinal direction of the vehicle. Therefore, the position ofthe input shaft, while keeping a required distance from the axles, canbe lower than that when being above the axles. Due to this arrangement,even if the amount of lubricating oil in the transmission housing issmall, splash lubrication for the input shaft can be sufficient.Consequently, the amount of lubricating oil can be saved, therebyreducing manufacturing costs and weight of the transmission. And, whenthe present invention is applied to a transmission of a truck, its deckcan be located at a low position, thereby improving capacity of the deckand sinking the center of gravity of the truck.

[0011] The transmission further comprises a drive train which can switchthe rotational direction of the output shaft in relation to therotational direction of the input shaft, wherein the drive traindrivingly connects the input shaft with a portion of the output shaft,which is nearer to one end of the output shaft, a prime rotary objectprovided on the output shaft nearer to other end of the output shaft, afollower rotary object serving as an input means of said differential,the follower rotary object being engaged with the prime rotary object,and a centrifugal governor for changing the output of the engineaccording to the variation of the rotational speed of the input shaft,the centrifugal governor being disposed at a portion of the input shaftfacing toward the prime rotary object. Therefore, by the adoption of thecentrifugal governor which is smaller and less expensive than a torquegovernor, manufacturing costs of the transmission can be saved andcompactness thereof can be improved. And, because the centrifugalgovernor is placed at empty space inside of the transmission housing, alayout of the transmission can be simple and space-saving, therebyfurther improving compactness of the transmission.

[0012] The transmission further comprises a pair of left and righttransmission housing parts into which the transmission housing islaterally dividable through a surface which is perpendicular to alongitudinal direction of said axles, wherein the differential issupported at its left and right portions by the left and righttransmission housing parts, respectively, and bearings provided at outerends of the respective axle housings, wherein the bearings supportoutward portions of the axles projecting leftward and rightward from thedifferential. Therefore, because the differential can be directlysupported by the transmission housing without intervention of the axles,when manufacturing of the transmission, a convenient assembling method(i.e., a method of putting in axles after fixing the differential to thetransmission housing by joining together of left and right housingparts) can be adopted. Furthermore, since outward portions of the axlesare supported by the axle housings through the bearings, the weight ofthe vehicle can be surely supported by the axles through the axlehousings.

[0013] A portion of at least one of said the housings to be attached tothe transmission housing is expanded so as to be bowl-like shaped. Thewet-type disc brake is disposed in the bowl-like shaped portion of theaxle housing, and an arm for operating the wet-type disc brake isdisposed outside the bowl-like shaped portion of the axle housing.Therefore, because a room which houses the wet-type disc brake (i.e. thebowl-like shaped portion) is integrally formed with the axle housing,manufacturing costs of the transmission can be reduced. And, because thearm for operating the wet-type disc brake is disposed outside the bowlportion of the axle housing, the operating system from the arm towet-type disc brake can be compactly and simply formed.

[0014] A transmission of a working vehicle comprises a differential, atransmission housing containing the differential, a pair of left andright axles connected with each other in a differential manner by thedifferential, an axle housing mounted onto one of left and right facesof the transmission housings to support one of the axles, wherein ajoint space is formed in a joint portion between the transmissionhousing and the axle housing, a differential locking slider which canswitch between a differential mode for connecting the left and rightaxles with each other in a differential manner and adifferential-locking mode for integrally connecting the axles, afriction disc provided on the axle supported by the axle housing, and apressure member which pushes the friction disc so as to brake the axle,wherein the pressure member and the differential locking slider aredisposed substantially coaxially with each other in the joint space.Therefore, the differential locking slider and the pressure member canbe arranged in a compact length of longitudinal direction of the axles,thereby contributing to space-saving of the transmission.

[0015] A guide portion for axially slidably supporting said pressuremember is provided in a flanged portion formed on an outer side wall ofthe transmission housing for mounting the axle housing, the differentiallocking slider is disposed in the guide portion, and a round wall of theguide portion is partly notched such that an arm for operating thedifferential locking slider is inserted through the notched portion.Therefore, because the pressure member is supported by the guide portionand the differential locking slider is located inside of the guideportion, both of them can be apportioned between inside and outside ofthe guide portion in a compact mass. And, because the round wall of theguide portion is partly notched and the arm for operating thedifferential locking slider is inserted through the notched portion, thesimple structure for operating the differential locking slider locatedin the guide portion from the outside of the guide portion can beachieved.

[0016] The pressure member is rotatable along said round wall of saidguide portion by a brake operating shaft supported by said axle housing,and a cam body, which thrusts the pressure member in correspondence toas rotational degree of the pressure member, is supported around theround wall of the guide portion. Therefore, since the pressure memberrotates while it is guided by an outer peripheral surface of the roundwall of the guide portion, a special structure for axial alignment ofthe pressure member can be eliminated. And, since the cam body issupported around the round wall of the guide portion, the compactstructure that the pressure member pushes the friction discs by axiallysliding while rotating can be achieved.

[0017] A rotational axis of the arm for operating the differentiallocking slider is disposed at a position which is offset from a virtualplane containing the rotational axis of said pressure member, and thebrake operating shaft is placed in parallel with the axles on a oppositeside to the arm with the virtual plane between. Therefore, an operatingsystem of the differential locking slider and an operating system of thebrake device can be compactly arranged and can avoid interruptions witheach other, thereby miniaturizing the transmission.

[0018] Furthermore, the transmission further comprises an input shaftprojecting outward from one of left and right sides of said transmissionhousing and a follower pulley constituting a belt-type CVT disposed ontoan outward projecting portion of the input shaft, wherein saiddifferential locking slider is disposed at a position nearer to theother of the left and right sides of the transmission housing.Therefore, an operating system of the differential locking slider can bedisposed in a position wherein the operating system can avoidinterruptions with the CVT, thereby improving the compactness of thetransmission.

BRIEF DESCRIPTION OF THE FIGURES

[0019]FIG. 1 is a general side view of a truck to which a transmissionof the present invention is applied.

[0020]FIG. 2 is a sectional rear elevation showing the general structureof the transmission and axles.

[0021]FIG. 3 is a grossly enlarged sectional rear elevation showing thestructure in a transmission housing.

[0022]FIG. 4 is a side view of the transmission.

[0023]FIG. 5 is a sectional side view of the transmission.

[0024]FIG. 6 is a sectional side view of the transmission when modifiedaxle housings are attached.

[0025]FIG. 7 is a general side view of a truck having a transmissionwherein a differential locking mechanism is provided.

[0026]FIG. 8 is a sectional rear development showing the structure in atransmission housing.

[0027]FIG. 9 is a perspective view showing the state wherein axlehousings are detached from a transmission housing.

[0028]FIG. 10 is a sectional rear view showing a transmission of thetype which receives power from an electric motor.

[0029]FIG. 11 is a segmentary perspective view showing the structure forholding friction discs to an axle housing in the brake device of thetransmission of electric motor type.

[0030]FIG. 12 is a grossly enlarged sectional rear development mainlyshowing the structure of a clutch fork shaft and an idle gear.

[0031]FIG. 13 is a sectional side view showing the structure that adifferential shift arm is inserted through a partly notched portion ofthe guide portion.

[0032]FIG. 14 is a sectional side view mainly showing the structure of adirection-switching shaft.

[0033]FIG. 15 is a perspective view showing a right housing membercomposing the transmission housing.

[0034]FIG. 16 is a perspective view showing a pressure member.

[0035]FIG. 17 is a sectional plan development showing brake controlshafts.

[0036]FIG. 18 is a sectional rear view showing the structure for leadinglubricating oil to an output shaft.

DETAILED DESCRIPTION OF THE INVENTION

[0037] A truck 1 as an embodiment of the present invention is shown inFIG. 1. A bodywork frame 10 is disposed in the longitudinal direction ofthe vehicle. An engine 3 is mounted on the bodywork frame 10 at the rearof an operator's seat 2. The engine 3 is disposed such that itscrankshaft (as an output shaft of the engine) 6 is horizontally orientedperpendicular to the longitudinal direction of the vehicle.

[0038] At the rear of the engine 3, a transmission 4 of the presentinvention is supported by the bodywork frame 10 through a pair of axlehousings 80 (described below). A pair of left and right slender flatboards are disposed in a longitudinal direction of the vehicle andparallel to each other, and the rear end portion of the flat boards areconnected with each other, thereby forming the bodywork frame 10 havinga U-shape in a plan view. As shown in FIG. 2, axle housings 80 are fixedonto the bodywork frame 10 such that a housing 31 of the transmission 4is located between the left and right flat boards.

[0039] A deck frame 10 a is disposed above the transmission 4 and theengine 3, and is supported by the bodywork frame 10, such that the truckcan carry loads.

[0040] An input shaft 5 of the transmission 4 projects leftward from thetransmission housing 31. The input shaft 5 is connected to the outputshaft 6 of the engine 3 through a belt-type automatically continuousvariable transmission (hereinafter referred to as CVT) 7. A pair of leftand right rear axles 8 project outward from both left and right sides ofthe transmission housing 31. Each of rear wheels 9 as drive wheels isprovided at the outer end of each of the rear axles 8.

[0041] A front transaxle case (not shown) is supported at a frontportion of the vehicle. The front transaxle case houses a pair of leftand right front axles 11, and a differential (not shown) which connectsthe front axles 11 with each other in a differential manner. Each of thefront axles 11 supports each of front wheels 12 at its outer end. Thefront wheels 12 are steerable by a steering wheel 13 disposed at thefront of the operator's seat 2.

[0042] A switching lever 19, which is operated to select the directionof travel between forward and backward, is disposed at the side of thesteering wheel 13. A speed-changing pedal 21 is provided at the front ofthe operator's seat 2, and is linked with a throttle valve (not shown)which adjusts the volume of injected fuel. By changing the degree ofopening of the throttle valve according to degree of depressing of thespeed-changing pedal 21, the output speed of the engine 3 can beincreased or reduced.

[0043] The power, which is transmitted from the output shaft 6 to theinput shaft 5 of the transmission 4 through the CVT 7, is transmittedinto the transmission housing 31 through the input shaft 5. The powerpasses through a power transmission way which forming the transmission4, and is finally transmitted to the rear wheels 9 through the rearaxles 8, thereby driving the truck 1.

[0044] A pair of brake devices (not shown in FIG. 1) are provided in theaxle housings 80 so as to brake the pair of left and right rear axles 8,respectively. Each of the brake devices 22 can be operated by each of apair of brake control arms 23 which are supported rotatably on each ofthe left and right axle housings 80. The brake control arms 23 areinterlocked with only one brake pedal (not shown) disposed in thevicinity of the speed-changing pedal 21, such that the left and rightrear axles 8 are braked at the same time by depressing the brake pedal.

[0045] Next, description will be given on the structure in thetransmission housing 31 in accordance with FIG. 2.

[0046] The transmission housing 31, which houses the transmission 4, isformed of a pair of left and right housing members 31L and 31R (servingas transmission housing parts) which are joined to each other at theirflat and peripheral joint faces in a plane which is perpendicular to alongitudinal direction of the rear axles 8. In the transmission housing31, the input shaft 5, a centrifugal governor 34 which detects therotational speed of the input shaft 5, a differential 32 which connectsthe left and right rear axles 8 in a differential manner, and adirection-of-travel switching mechanism 35 operated by the switchinglever 19, and so on are disposed.

[0047] The input shaft 5 is laterally and rotatably supported at themidway portion in a vertical direction of the transmission housing 31.One end of the input shaft 5 projects laterally outward from a left sideof the transmission housing 31. A follower split pulley 36 is providedon the outward projecting portion of the input shaft 5, such that thefollower split pulley 36 serves as an output section of above-mentionedbelt-type CVT 7.

[0048] The follower split pulley 36 is formed of two pulley members 36 aand 36 b which are connected with each other forming torque cam as shownin FIG. 3. The two pulley members 36 a and 36 b approach each other whentorque which resists the rotation of the engine 3 (e.g. torque generatedat the rear wheels 9 when the truck 1 climbs a hill) increases, suchthat an effective diameter of the follower split pulley 36 increases soas to increase the speed reduction ratio of the CVT 7.

[0049] Next, description will be given on the centrifugal governor 34.

[0050] This centrifugal governor 34, disposed around a portion of theinput shaft 5 facing toward a later-discussed output gear 51, comprisesa governor weight 71, a lifter 72, a governor fork 73, a rotation shaft74 and an output arm 75. The governor weight is a sensor which isrotated outward according to centrifugal force so as to detect therotational speed of the input shaft 5. The lifter 72 is slidden axiallyat the same time when the governor weight 71 rotates outward. Thegovernor fork 73 is engaged with the lifter 72. The rotation shaft 74 issupported rotatably at the ceiling of the transmission housing 31. Theoutput arm 75 is disposed on the outside of the transmission housing 31so as to rotate integrally with the rotation shaft 74.

[0051] The output arm 75 is interlocked with the throttle valve of theengine 3 through a linkage, such that the centrifugal governor 34detects the rotational speed of the input shaft 5 and adjusts the volumeof injected fuel, thereby changing the output of the engine 3 accordingto the variation of the rotational speed of the input shaft 5.

[0052] Next, description will be given on the direction-of-travelswitching mechanism 35 serving as a drive train to allow switching therotational direction of the output shaft 37 in relation to therotational direction of the input shaft 5.

[0053] The input shaft 5 is notched on its periphery so as to form twogears, i.e., a forward drive gear 39 and a reverse drive gear 40. Theoutput shaft 37 is disposed parallel to the input shaft 5 (and the rearaxles 8). Around a portion of the output shaft 37 which is nearer to theleft end of the output shaft 37, a forward follower gear 43 isrelatively rotatably disposed, and a clutch gear 44 are not relativelyrotatably but axially slidably disposed. The forward follower gear 43,which is constantly engaged with the forward drive gear 39, is notchedon its side face so as to form a toothed portion 43 a, thereby beingengaged/disengaged with/from a toothed portion 44 a formed on the sideface of the clutch gear 44 facing the toothed portion 43 a.

[0054] An idle gear 45, designated by a phantom line in FIG. 3, isconstantly engaged with the reverse drive gear 40. The clutch gear 44also can be engaged/disengaged with/from the idle gear 45.

[0055] The clutch gear 44 is axially slid so as to engage with eitherthe forward follower gear 43 or the idle gear 45, thereby selectivelybringing the output shaft 37 into a regularly directed rotation or areversely directed rotation.

[0056] As shown in FIG. 5, a clutch fork shaft 48 is straightly,slidably disposed adjacent to the clutch gear 44, and a clutch fork 49is fixed onto the clutch fork shaft 48 and is engaged with the clutchgear 44. A control shaft 60 is vertically and rotatably supported at theceiling of the transmission housing 31 so as to slide the clutch forkshaft 48. An arm 61 is fixed onto a bottom portion of the control shaft60 and an apex portion of the arm 61 is engaged with a groove formed onthe clutch fork shaft 48. A top portion of the control shaft 60 projectsupward, and an operating arm 62 is fixed onto the upward projectingportion of the control shaft 60. The operating arm 62 is interlockedwith the above-mentioned switching lever 19, thereby allowing the clutchgear 44 to slide to a forward position or a backward position.

[0057] A portion of the output shaft 37, which is nearer to the rightend of the output shaft 37, is notched on its periphery so as to formthe output gear 51 serving as a prime rotary object, therebytransmitting the rotation of the output shaft 37 to the differential 32.

[0058] The differential 32 is constructed normally for differentiallyconnecting inner end portions of the pair of rear axles 8, which extendoppositely to each other. In detail, as shown in FIG. 3, thedifferential 32 comprises a hollow differential casing 52, a ring gear53, a pinion shaft 54, two pinions 55, and two differential side gears56. The differential casing 52 is disposed coaxially with the rear axles8, and rotatably supported at its left and right portions by the leftand right housing members 31L and 31R through bearings 111,respectively. The ring gear 53, serving as a follower rotary object, isfixed around the differential casing 52 and is engaged with the outputgear 51 of the output shaft 37. The pinion shaft 54 is disposed in thedifferential casing 52 perpendicular to the rear axles 8 so as to berotatable integrally with the differential casing 52. The pinions 55,which are bevel gears, are disposed oppositely to each other androtatably supported on the pinion shaft 54. Each of the differentialside gears 56 which are bevel gears is fixed onto an inner end of eachof the rear axles 8 so as to engage with both the pinions 55.

[0059] Next, the axle housings 80, each of which supports each of therear axles 8, will be described.

[0060] The two axle housings 80 are formed in the same cylindricalshape. As shown in FIG. 2, an inner end of each of the axle housings 80is symmetrically fixed onto each of left and right sides of thetransmission housing 31, so as to cover an opening portion formed oneach of the left and right side faces of the transmission housing 31. Anouter end of each of the axle housings 80 projects outward along therear axles 8. A supporting portion is formed at the projecting endportion of each of the axle housings 80 so as to support an outwardportion of each of the rear axles 8 by a bearing 110. Thus, a portion ofeach rear axle 8 adjacent to its proximal end is covered at a certainlength with each axle housing 80.

[0061] A top portion of the supporting portion of each of the axlehousings 80 is formed into a mounting portion 80 a having a horizontallyflat shape. The mounting stay 81 in a flat-board-like shape, which isfixed onto a bottom end of the bodywork frame 10, is fixed onto themounting portion 80 a by screwing bolts so as to support the axlehousings 80 by the bodywork frame 10. In such a structure, a loadapplied to the rear wheels 9 can be supported by the transmissionhousing 31 through the axle housings 80, thereby simplifying thestructure of a vehicle.

[0062] As shown in FIG. 3, left and right brake devices 22, for brakingthe rear axles 8, is provided around portions of the rear axles 8covered by the axle housings 80, respectively. Portions of the axlehousings 80 to be attached to the transmission housing 31 are expandedso as to be bowl-like shaped. Each of brake devices 22 is housed in eachof bowl-like shaped portions 80 b.

[0063] In each of the brake devices 22, first friction disc 91 areaxially slidably but not relatively rotatably provided onto the rearaxle 8. And, second friction discs 92 are slidably but not relativelyrotatably engaged with the axle housing 80.

[0064] Each of the first friction discs 91 and each of the secondfriction discs 92 are arranged alternately. A pressure member 93 isfitted axially slidably and rotatably onto the transmission housing 31for pressuring the multi-layered friction discs 91 and 92. Cam groovesare formed on the pressure member 93, and each of steel balls 94,serving as cam bodies, is intervened between each of the cam grooves andthe axle housing 80. A brake control shaft 96 is rotatably supported bythe axle housing 80, and a cam is formed at one end portion of a brakecontrol shaft 96 in a D-shape (not shown) so as to push an arm 95 formedat a top portion of the pressure member 93. The above-mentioned brakecontrol arm 23 is fixed onto one end of the brake control shaft 96,which projects outward from the axle housing 80. The brake control arm23 is disposed outside above-mentioned bowl-like shaped portion 80 b.

[0065] In this structure, when the brake control arm 23 is operated, thebrake control shaft 96 is rotated and the above-mentioned D-shape campushes the arm 95 so as to rotate the pressure member 93. By the actionof cam between the cam groove and the steel ball 94, the pressure member93 is slidden axially and make the friction discs 91 and 92 engage withone another, thereby braking the rear axle 8.

[0066] The axle housings 80 and the transmission housing 31 are filledwith oil, i.e., the brake devices 22 are of a wet type, thereby beingimproved in its durability and reliability.

[0067] The input shaft 5 is displaced from a position above the rearaxles 8 so as to be nearer to the engine 3 than the rear axles 8 in thelongitudinal direction of the vehicle such that the position of theinput shaft 5 can be lowered in the transmission housing 31.Consequently, even if the amount of the filled oil is small and oillevel OL is low, splash lubrication for the input shaft 5 by therotation of the ring gear 53 of the differential 32 can be sufficientbecause the input shaft 5 is located at the low position.

[0068] Various modification of the above-mentioned embodiment ispossible. For example, as shown in FIG. 6, the structure that axlehousings 80′ are fixed onto the transmission housing 31 leaning forwardor backward so as to locate the brake control arm 23 at a low position,may be available.

[0069] Next, description will be given on a transmission 4′ wherein adifferential locking mechanism is provided. A truck to which thetransmission 4′ is applied is shown in FIG. 7.

[0070] As shown in FIGS. 8 and 9, each of the left and right housingmembers 31L and 31R is formed at its outer side wall into each of leftand right cylindrically flanged portions 31La and 31Ra which areextended laterally outward. The outer end surface of each of thecylindrically flanged portions 31La and 31Ra is formed into a verticalflat joint face, on which the above-mentioned axle housing 80 ismounted.

[0071] As shown in FIG. 8, a hole 97 is formed on the side wall of theright housing member 31R, and one end portion of an input shaft 5′ ofthe transmission 4′ is supported in the hole 97 through a bearing. Asshown in FIG. 10, a mounting surface 98, onto which an electric motor 99is mounted through a bracket 100, is formed on an outer face of the sidewall around of the hole 97 of the right housing member 31R. Namely, thehousing members 31L and 31R are available for both of an engine type andan electric motor type. Reference numerals 101 in FIGS. 8 and 9designate as mounting bosses formed on the right housing member 31R forscrewing the bracket 100 onto the mounting surface 98.

[0072] In the engine type shown in FIG. 8, which receives power from theengine 3 through the CVT 7, the input shaft 5′ projects outward throughthe side wall of the left housing member 31L, and the hole 97 in theright housing member 31R is closed by a cover 102.

[0073] On the other hand, in the electric motor type shown in FIG. 10,an input shaft 5″ projects outward through the hole 97 and is connectedwith a motor shaft 103 of the electric motor 99 through a coupler 104.In this type, a cover 106 closes a hole 105 in the left housing member31L.

[0074] In the electric motor type, the direction-of-travel switchingmechanism 35 (as provided in the engine type) is removed, and the inputshaft 5″ and an output shaft 37′ are constantly engaged with each otherthrough a gear 44′. Because, the electric motor 99 itself can bring theinput shaft 5″ into a regularly directed rotation or a reverselydirected rotation selectively.

[0075] The engine type will be described in accordance with FIGS. 12 andgreater. As shown in FIG. 12, the idle gear 45 in thedirection-of-travel switching mechanism 35 is supported rotatably on ashaft 14. A left end of the shaft 14 is supported by a boss formed onthe inner face of the side wall of the left housing member 31L. As shownin FIGS. 12, 14, and 15, the joint surface, which is formed on the lefthousing member 31L to join with the right housing member 31R, partlyprojects inward of the transmission housing 31. A support plate 30 isscrewed to the projected portion, and a right end of the shaft 14 isinserted and fitted into a circular hole 30 a formed in the supportplate 30.

[0076] In this structure, the shaft 14 is rattle-free because the bothends of the shaft 14 are supported. And, the shaft 14 is not required tobe so long as a whole width of the transmission housing 31, therebyimproving compactness. Other mechanics (in this embodiment, the rotationshaft 74 and the governor fork 73 of the centrifugal governor 34) can beplaced in such formed empty space.

[0077] As shown in FIGS. 8 and 12, a forward follower gear 43 and abackward follower gear 44 are relatively rotatably supported around theoutput shaft 37′. The forward follower gear 43 is constantly engagedwith the forward drive gear 39 formed around the input shaft 5′, andbackward follower gear 44 is with the reverse drive gear 40 through theidle gear 45.

[0078] Between the two follower gears 43 and 44, a clutch slider 47 isnot relatively rotatably but axially slidably disposed around the outputshaft 37′. The clutch slider 47 is axially slidden so as to engage witheither the forward follower gear 43 or backward follower gear 44,thereby selectively bringing the output shaft 37′ into a regularlydirected rotation or a reversely directed rotation. Also, the clutchslider 47 can be located at its neutral position where it engages withnone of the two gears 43 and 44.

[0079] The clutch fork shaft 48 is straightly slidably supported by thetransmission housing 31, as shown in FIG. 12. The clutch slider 47 isengaged with the clutch fork 49 which is fixed onto the midway portionof the clutch fork shaft 48.

[0080] As shown in FIGS. 9 and 14, a direction-switching shaft 50 isvertically supported at the ceiling of the right housing member 31R. Anarm 46 is fixed onto the end portion of the direction-switching shaft 50in the transmission housing 31. An apex end portion of the arm 46 isengaged with the groove notched on a midway portion of the clutch forkshaft 48. The speed-changing lever (not shown), which is interlockedwith the switching lever 19 provided beside the operator's seat 2 ofvehicle, is fixed onto an external-of-housing end portion of thedirection-switching shaft 50.

[0081] In the above structure, the clutch slider 47 can be slidden amonga forward-driving position, a backward-driving position and a neutralposition according to operation of the switching lever 19.

[0082] A detent mechanism 66 is provided with the clutch fork shaft 48to keep its operating positions. The detent mechanism 66 comprises threegrooves 48 a notched on the clutch fork shaft 48 in correspondence tothe above-mentioned three operating positions (the forward-drivingposition, the backward-driving position and the neutral position), and adetent ball 67 biased by spring so as to engage with one of the threegrooves 48 a.

[0083] An electrical switch 68 is provided with the clutch fork shaft 48so as to detect its neutral position. The switch 68 is electricallyconnected with a circuit for starting a cell motor of the engine 3,thereby allowing the engine 3 to start only when the clutch fork shaft48 is located in its neutral position.

[0084] Next, description will be given on a differential 32′. Thedifferential 32′ is constructed almost similarly with the differential32 of above-mentioned embodiment, except that a differential lockingmechanism 33 is provided.

[0085] The differential locking mechanism 33 is provided for locking thedifferential 32′. As shown in FIG. 8, a differential locking slider 57is axially slidably provided around the right rear axle 8 on theopposite side to the differential casing 52 with the ring gear 53between. A dog clutch portion 58 is formed on the surface of thedifferential locking slider 57 facing the ring gear 53. An engagingportion 59 is formed at a boss of the ring gear 53 so as to engage withthe dog clutch portion 58.

[0086] In this structure, the differential locking mechanism 33 can beselected among the differential-locked mode wherein the dog clutchportion 58 is engaged with the engaging portion 59 and the differentialcasing 52 is connected integrally with the left and right rear axles 8,and the differential-unlocked mode wherein the dog clutch portion 58 isdisengaged from the engaging portion 59 and the differential 32′connects the rear axles 8 in a differential manner.

[0087] As shown in FIGS. 9 and 13, a differential control shaft 63 isrotatably and vertically supported by the right housing member 31R. Adifferential shift arm 64, the apex end of which is engaged with thedifferential locking slider 57, is fixed onto one end of thedifferential control shaft 63 which projects in an inward direction ofthe transmission housing 31.

[0088] A differential locking control arm 65 is fixed onto one end ofthe differential control shaft 63 which projects in an outward directionof the transmission housing 31. The differential locking control arm 65is connected to the differential-locking operating tool (not shown)provided beside the operator's seat 2 through a linkage etc., therebyallowing operating to bring the differential 32′ into either a lockedmode or an unlocked mode.

[0089] Next, the brake devices 22′ in this embodiment will be described.

[0090] As shown in FIG. 8, the boss of the ring gear 53 is supported bythe side wall of the right housing member 31R, and a boss of thedifferential casing 52 is by the side wall of the left housing member31L. Both of the side walls project cylindrically in an outwarddirection, thereby forming above-mentioned flanged portions 31La and31Ra. The cylindrically flanged portions 31La and 31Ra, formed formounting the axle housing 80, forms its internal space into empty space(hereafter referred to as ‘jointing space’).

[0091] Besides, in above-mentioned ‘jointing space’, left and rightouter walls of the housing members 31L and 31R project cylindrically ina laterally outward direction, thereby forming guide portions 31Lb and31Rb. A pair of left and right pressure members 93 are fitted around theguide portions 31Lb and 31Rb respectively, and supported relativelyrotatably and axially slidably. Each of the pressure members 93 has aring-shape as shown in FIG. 16, and its internal diameter is equal to anexternal diameter of the guide portions 31Lb and 31Rb. Two hooks 93 aare formed on the external periphery of each of the pressure members 93.

[0092] The differential locking slider 57 is placed in the guideportions 31Rb of the right housing member 31R.

[0093] As shown in FIGS. 8, 9, 13, and 17, a pair of brake controlshafts 96 are rotatably supported above the pressure members 93 inparallel with the rear axles 8. An inner end portion of each of brakecontrol shafts 96 is supported by a boss 17 formed on the side wall ofeach of left and right housing members 31L and 31R. An outer end portionof each of the brake control shafts 96 is supported by each of the axlehousings 80 and projects outward. The above-mentioned brake control arm23 is fixed onto the outward projecting portion of the brake controlshaft 96.

[0094] As shown in FIG. 13, a midway portion of the brake control shaft96, which faces one of the two hooks 93 a of the pressure member 93, isformed into a cam having a D-shape. In this structure, when the brakecontrol arm 23 is operated and the brake control shaft 96 are rotated,the cam pushes the hook 93 a, thereby the pressure member 93 is rotatedaround the guide portion 31Lb (31Rb).

[0095] As shown in FIG. 8, a plurality of depressions, each of which isformed into a hemispherical shape, are arranged at regular intervals incircumference on the side wall of the left housing member 31L at theoutside of the guide portion 31Lb. And, as shown in FIGS. 8 and 13, aplurality of ball retaining portions 70 project from the side wall ofthe right housing member 31R in correspondence to above-mentioneddepressions. A depression, having a hemispherical shape, is formed oneach of the ball retaining portions 70.

[0096] In correspondence to the position of the depressions, a pluralityof depressions 93 b are formed and arranged at regular intervals incircumference on one side face as shown in FIG. 16. Each of thedepressions 93 b looks like a lozenge in a side view and like a cone ina sectional view, such that the depth of the depression 93 b is thegreatest at a center portion in circumference.

[0097] A steel ball 94 is supported by each of the hemisphericaldepressions of the housing member 31L (31R), and the pressure member 93is fitted around the guide portion 31Lb (31Rb) such that each of thesteel balls 94 is fitted into each of the depressions 93 b. The each ofabove-mentioned friction discs 91 and 92 are disposed between the otherside face of the pressure member 93 and the inner side face of the axlehousing 80.

[0098] In this structure, when the pressure member 93 is rotated alongan outer peripheral surface of the guide portion 31Lb (31Rb) by theoperation of brake control arm 23, the pressure member 93, onto whichthe cam action of the steel balls 94 is applied, gets thrust (greater asits rotational degree increases) and is slidden outward, therebypressuring the friction discs 91 and 92 and braking the rear axles 8.

[0099] A projection 92 a is formed at a portion of each disc of thesecond multi friction discs 92. Each of these projections 92 a isengaged with a recess formed on inner surface of the axle housing 80. Asshown in FIGS. 8 and 9, a holding hook 107 is fixed in the vicinity ofthe recess. An apex end of the holding hook 107 holds the projection 92a of an innermost disc of the second friction discs 92.

[0100] In above structure, when manufacturing of the transmission 4′,each of the brake devices 22′ can be installed in the each of the axlehousings 80, and the holding hook 107 can prevent the friction discs 91and 92 from being detached from the axle housing 80, thereby forming anassemblage of axle housing 80 and brake device 22′ as shown in FIG. 9.Therefore, the transmission 4′ can be simply assembled by mounting leftand right such assemblages on the transmission housing 30.

[0101] Instead of the holding hook 107, the structure that an elasticwire having a U-like shape is fitted into two holes formed on the axlehousing 80 such that the wire strides the projection 92 a, is available.This structure is applied on the above-mentioned electric motor type asshown in FIGS. 10 and 11.

[0102] In this electric motor type, a distance between the two holes 109formed on the axle housing 80 is a little shorter than a distancebetween both ends of the wire 108. Thus, when the wire 108 is fittedinto two holes 109, the wire transforms such that its both ends approacheach other. A friction force is generated between the fitted wire 108and the two holes 109 by an elasticity of the wire 108 such that thewire 108 does not detach from the axle housing 80 and can hold thefriction discs 91 and 92 of the brake device 22′.

[0103] The guide portion 31Rb is formed wider than the guide portion31Lb, and the external diameter of the differential locking slider 57 issmaller than the internal diameter of the guide portion 31Rb (namely,smaller than the internal diameter of the pressure member 93). Thedifferential locking slider 57 is provided at the inner space of theguide portion 31Rb, and is overlapped with the pressure member 93 in alongitudinal direction of the rear axles 8.

[0104] In this structure, the pressure member 93 and the differentiallocking slider 57 are provided in the above-mentioned ‘jointing space’.And, because each of the guide portions 31Lb and 31Rb is cylindricallyformed coaxially with a rotational axis of the rear axles 8, therotational axis of the pressure member 93 is substantially coaxial withan axis of the differential locking slider 57 provided on the rear axle8.

[0105] Thus, the differential locking slider 57 and the pressure member93 can be disposed in a compact mass, thereby enhancing, thetransmission 4′ in its compactness.

[0106] As shown in FIGS. 8 and 13, the differential locking slider 57 isdisposed at inner space of the guide portion 31Rb of the right housingmember 31R. As shown in FIGS. 9 and 13, the guide portion 31Rb is formedsuch that its cylindrical wall is partly notched, thereby forming anopening portion 15. The differential shift arm 64 is inserted throughthe opening portion 15, and an apex portion of the differential shiftarm 64 is engaged with the differential locking slider 57.

[0107] As shown in FIG. 13, the differential control shaft 63, ontowhich the differential shift arm 64 is fixed, is disposed at a positionwhich is offset from a virtual plane P containing the rotational axis ofthe pressure member 93. Therefore, the rotational axis of thedifferential control shaft 63 and the rotational axis of thedifferential shift arm 64 are disposed in skewed direction with eachother and do not cross.

[0108] Thus, the differential locking slider 57 can be slidden throughthe rotation of the differential control shaft 63 and the differentialshift arm 64. The only small space needed for rotation of thedifferential shift arm 64 is sufficient for operating the differentiallocking slider 57 in the transmission housing 31.

[0109] On the other hand, in the structure that the differential lockingslider 57 is engaged with a shift fork which is slidden straightly, alarge space is needed for shifting the shift fork, thereby inhibitingminiaturization of the transmission. The structure of this embodimentsolves this issue.

[0110] In this embodiment, the brake control shaft 96 is placed on theopposite side to the differential control shaft 63 with the virtualplane P between. By this layout, a differential-locking operating systemand a brake operating system can be disposed in a compact mass, and alsocan avoid interruptions with each other.

[0111] As shown in FIG. 8, the cylindrical flanged portion 31Ra and theguide portion 31Rb of the right housing member 31R are formed wider thanthe portions 31La and 31Lb of the left housing member 31L, because thedifferential locking slider 57.is disposed in the guide portion 31Rb. Asshown in FIGS. 9 and 13, the electrical switch 68, the differentialcontrol shaft 63, and a breather cap 16 for bleeding of air are disposedat the widely-formed cylindrical flanged portion 31Ra, thereby achievingthe rational layout for miniaturization of the transmission 4′.

[0112] In this embodiment, each of the axle housings 80 is formedsymmetrically with respect to the virtual vertical plane which includesthe axis of the rear axles 8. Thus, two members of uniform shape can beused for both of left and right axle housings 80, thereby reducing theirmanufacturing costs.

[0113] Furthermore, a pair of front and rear holes, formed on side wallsof the respective axle housings 80, are arranged symmetrically withrespect to above-mentioned virtual vertical plane. And, in the structurethat axle housings 80 are disposed left and right, each of the frontholes supports each of left and right brake control shafts 96, and eachof the rear holes is covered by a cap 86 as shown in FIG. 9. Thus, theleft and right brake control shafts 96 can be coaxially disposed, andleft and right brake systems can be rationally symmetrically arranged.

[0114] Furthermore, two hooks 93 a, formed on each of the pressuremembers 93, are arranged symmetrically as shown in FIG. 16. Thus, twomembers of uniform shape can be used for both of left and right pressuremembers 93, thereby reducing their manufacturing costs.

[0115] Next, the structure for lubrication of the transmission 4′ willbe described.

[0116] The transmission housing 31 is filled with lubricating oil inestablished amount, and an oil level OL is determined as shown in FIG.14. In this state, when the transmission 4′ is driven and the ring gear53 and a forward follower gear 43 rotate in the direction designating asa bold arrow in FIG. 14, the oil is splashed on the input shaft 5′ andthe output shaft 37, which are disposed at upward slant position of thering gear 53.

[0117] As shown in FIGS. 14 and 18, a trough portion 24, having aV-shape in an interior side view, is formed on an inner face of sidewall of the right housing member 31R. An oil leading hole 76 is formedin a horizontal direction on the portion of the right housing member 31Rwhich faces a base of the trough portion 24. The oil leading hole 76communicates with a connecting hole 77, which is formed vertically inthe side wall of the right housing member 31R. The connecting hole 77 isconnected with a groove 78, which is formed in a boss of the righthousing member 31R for supporting an end of the output shaft 37′.

[0118] In this structure, a part of the splashes of oil by rotation ofthe ring gear 53 etc. reaches above the trough portion 24, and flowsalong the oil leading hole 76 and the connecting hole 77 and is led tothe groove 78, thereby lubricating a bearing which supports the outputshaft 37′. And, a part of the oil flows along an oil path (designated asa reference numeral 87 in FIG. 12), and lubricates the peripheralsurface of the output shaft 37′ for rotatably supporting the followergears 43 and 44, and a engaging portion of the clutch slider 47.

[0119] As shown in FIGS. 14 and 18, a lubricating inlet 82 is disposedjust above the trough portion 24. Therefore, when a cap 20 is taken offand lubricating oil is run in through the lubricating inlet 82, all thelubricating oil falls into the trough portion 24. A part amount of thelubricating oil can surely reach the groove 78 through the oil leadinghole 76 and the connecting hole 77 and can lubricate the bearingsupporting the output shaft 37′ and so on.

[0120] In this structure, even if components (e.g. the bearing forsupporting the output shaft 37, the follower gears 43 and 44, the clutchslider 47) are not spread with the lubricating oil in advance ofassembling the transmission 4′, these components are surely lubricatedby only running the oil in through the lubricating inlet 82 afterassembling the transmission 4′. Therefore, the number of man-hours formanufacturing can be reduced.

[0121] A hole 27 is formed at the bottom of side wall of the righthousing member 31R as shown in FIG. 13. An inner space of thetransmission housing 31 and an inner space of the right axle housing 80communicate with each other through the hole 27 such that the oil withwhich both the inner space are filled can circulate between.

[0122] Furthermore, two holes 25 and 26 are formed at the top of sidewall of the right housing member 31R. An inner space of the transmissionhousing 31 and an inner space of the right axle housing 80 alsocommunicates with each other through the two holes 25 and 26 such thatthe air in both the inner space can circulate between. Thus, the air inthe right axle housing 80 can be exhaled from the breather cap 16disposed on the transmission housing 31.

[0123] Similarly, holes are formed on the side wall of the left housingmember 31L (not shown). Therefore, the oil and air can circulate betweenthe inner space of the transmission housing 31 and an inner space of theleft axle housing 80.

[0124] As shown in FIG. 13, the breather cap 16 is disposed at theceiling portion of the right housing member 31R. An opening portion 83for installing the breather cap 16 is separated off by an inner wall 84from the inner space of the transmission housing 31, and a small hole 85is formed on the inner wall 84.

[0125] In this structure, the air in the transmission housing 31 cancommunicate with the atmosphere through the small hole 85 and thebreather cap 16. And, even if the oil filled with the transmissionhousing 31 is stirred and splashed around, a splash of the oil isblocked by the inner wall 84 before reaching the breather cap 16,thereby preventing oil-leak from the breather cap 16.

[0126] Although the invention has been described in its preferred formwith a certain degree of particularity, it is understood that thepresent disclosure of the preferred form may be changed in the detailsof construction, and the combination and arrangement of parts may bechanged or altered without departing from the spirit and the scope ofthe invention as hereinafter claimed.

What is claimed is:
 1. A transmission of a working vehicle having anengine mounted on a bodywork frame such that a crankshaft of the engineis horizontally oriented perpendicular to the longitudinal direction ofthe vehicle, comprises: an input shaft for receiving power of the enginethrough a continuously variable transmission; an output shaft disposedin parallel with said input shaft; a pair of left and right axlesextended oppositely to each other and in parallel with said outputshaft; a differential connecting said left and right axles with eachother in a differential manner; a transmission housing containing saidinput shaft, said output shaft, said pair of axles and saiddifferential; a pair of left and right axle housings mounted onto leftand right faces of said transmission housing respectively, said pair ofleft and right axle housings house said pair of left and right axles,and wherein said pair of left and right axle housings include mountingportions for mounting to the bodywork frame; and a wet-type disc brakedevice provided around a portion of said left and right axles covered bysaid left and right axle housings.
 2. The transmission of a workingvehicle as set forth in claim 1, wherein said input shaft is displacedcloser to the engine than said axles in the longitudinal direction ofthe vehicle.
 3. The transmission of a working vehicle as set forth inclaim 1, further comprising: a drive train which can switch therotational direction of said output shaft in relation to the rotationaldirection of said input shaft, wherein said drive train drivinglyconnects said input shaft with a portion of said output shaft, and whichis nearer to one end of said output shaft; a prime rotary objectprovided on said output shaft nearer to the other end of said outputshaft; a follower rotary object serving as an input means of saiddifferential, said follower rotary object being engaged with said primerotary object; and a centrifugal governor for changing the output of theengine according to the variation of the rotational speed of said inputshaft, said centrifugal governor being disposed at a portion of saidinput shaft facing toward said prime rotary object.
 4. The transmissionof a working vehicle as set forth in claim 1, further comprising: a pairof left and right transmission housing parts into which saidtransmission housing is laterally dividable through a surface which isperpendicular to a longitudinal direction of said axles, wherein saiddifferential is supported at its left and right portions by said leftand right transmission housing parts, respectively; and bearingsprovided at outer ends of said respective axle housings, wherein saidbearings support outward portions of said axles projecting leftward andrightward from said differential.
 5. The transmission of a workingvehicle as set forth in claim 1, wherein a portion of at least one ofsaid axle housings to be attached to said transmission housing isexpanded so as to be bowl-like shaped, wherein said wet-type disc brakeis disposed in the bowl-like shaped portion of said axle housing, andwherein an arm for operating said wet-type disc brake is disposedoutside the bowl-like shaped portion of said axle housing.
 6. Atransmission of a working vehicle, comprising: a differential; atransmission housing containing said differential; a pair of left andright axles connected with each other in a differential manner by saiddifferential; an axle housing mounted onto one of left and right facesof said transmission housing to support one of said left and rightaxles, wherein a joint space is formed in ajoint portion between saidtransmission housing and said axle housing; a differential lockingslider which can switch between a differential mode for connecting saidleft and right axles with each other in a differential manner and adifferential-locking mode for integrally connecting said left and rightaxles; a friction disc provided on at least one of said left and rightaxles and housed by said axle housing; and a pressure member whichpushes said friction disc so as to engage said at least one of said leftand right axles with said axle housing, thereby braking said at leastone of said left and right axles, wherein said pressure member and saiddifferential locking slider are disposed substantially coaxially witheach other in said joint space.
 7. The transmission of a working vehicleas set forth in claim 6, wherein: a guide portion for axially slidablysupporting said pressure member is provided in a flanged portion formedon an outer side wall of said transmission housing for mounting saidaxle housing, said differential locking slider is disposed in said guideportion, and a round wall of said guide portion is partly notched,forming a notch portion such that an arm for operating said differentiallocking slider is inserted through said notched portion.
 8. Thetransmission of a working vehicle as set forth in claim 7, wherein: saidpressure member is rotatable along said round wall of said guide portionby a brake operating shaft supported by said axle housing, and a cambody, which thrusts said pressure member in correspondence to asrotational degree of said pressure member, is supported around saidround wall of said guide portion.
 9. The transmission of a workingvehicle as set forth in claim 8, wherein: a rotational axis of said armfor operating said differential locking slider is disposed at a positionwhich is offset from a virtual plane containing the rotational axis ofsaid pressure member, and said brake operating shaft is placed inparallel with said left and right axles on a opposite side to said armwith the virtual plane between.
 10. The transmission of a workingvehicle as set forth in claim 6, further comprising: an input shaftprojecting outward from one of left and right sides of said transmissionhousing; and a follower pulley constituting a belt-type continuouslyvariable transmission disposed onto an outward projecting portion ofsaid input shaft, wherein said differential locking slider is disposedat a position nearer to the other of said left and right sides of saidtransmission housing.